1. Field of the Invention
The present invention relates to infrared flares, and more particularly, to infrared flare compositions which employ readily available fluorocarbon resins in the formation of the binder.
2. Description of the Prior Art
Fluorocarbon-magnesium mixtures are widely used in infrared flares since the reaction EQU (CF.sub.2)+Mg.fwdarw.MgF.sub.2(g) +C.sub.(S)
is high in enthalpy release, and produces carbon which emits strongly in the 1-2 micron region. Current flare compositions generally employ polytetrafluoroethylene or a mixture of polytetrafluoroethylene and vinylidene fluoride-hexafluoropropylene copolymer as the fluorocarbon material, such that the compositions must generally be pressed or extruded. Pressing and extrusion are less desirable than casting because they cannot be conveniently used to manufacture center perforate grains, nor grains of large or irregular shapes. Moreover, pressed charges burn more rapidly and less reproducibly than cast or tamp-cast compositions in which the binder wets the solid material. Pressing, and to a lesser extent extrusion, may also alter the particle size of crystalline ingredients, such as an oxidizer, in a non-uniform fashion.
The known curable liquid fluorocarbon binders are extremely expensive and are only available in very limited quantities. Thus, systems which employ such binders have had very limited use.
Accordingly, a need exists for a composition which is either pour-castable, i.e., it has a viscosity of less than 5.times.10.sup.5 centipoise, or is more readily used than the prior art as a cast-moldable or tampable composition, is curable to a shaped flare candle at moderately elevated temperatures, and yet is simple and inexpensive to produce.
Various flare compositions are known in the prior art which employ high molecular weight copolymers of vinylidene fluoride and hexafluoropropylene as a part of the matrix binder in conjunction with another material. However, such compositions either use chlorinated compounds which reduce the fluorine content, or use expensive and difficult to obtain fluorocarbon monomers in the formation of the binder. Typical of such prior art are the compositions described in U.S. Pat. Nos. 3,983,816; 3,640,785; 3,629,020; and 3,770,525. In addition, numerous patents discuss the use of copolymers of vinylidene fluoride and hexafluoropropylene, including U.S. Pat. Nos. 3,765,334; 3,732,132; and 3,734,788.